This invention relates to the processing of photographic materials. In particular, the invention simplifies the chemical processing of silver halide materials and reduces the volumes of liquid processing solutions employed.
Normally, silver halide materials are processed in equipment with deep tanks containing processing solutions. The solutions need to be maintained in a chemically stable state to the extent that uniformity and consistency of photographic results are assured.
The effects of evaporation, interaction with atmospheric gases such as oxygen and carbon dioxide, and the effects of processing usually have to be compensated for by replenishment techniques. This requires operator intervention and/or the provision of additional solutions and means of adding them accurately. Also liquid effluent is produced which has to be disposed of in a safe and cost-effective way. Such wet chemical systems are generally difficult to keep clean.
Low silver materials have been described which use small fractions of the amount of silver needed to provide the oxidation of developer resulting from development of the silver halide crystals when that oxidised developer is used to provide the image dye via reaction with colour-forming couplers. These low silver materials are processed in the presence of oxidising agents such as hydrogen peroxide in development amplification processes commonly referred to as Redox Amplification or RX processes. In such processes the developed silver image is used to catalyse in an image-wise manner, the production of oxidised developer and hence, image dye. Such materials are appropriate for print production.
It is possible to leave the developed silver in the image with little effect on image quality when very low amounts of silver halide are used (Research Disclosure, September 1997, p.638 ). It has also been suggested that it is possible to leave the silver halide in non-image areas. The silver halide can be stabilised to degradation by light, for example, by destroying the silver halide spectral sensitising dyes by exposure to light ( U.S. Pat. No. 5,441,843 ) or by converting the silver halide to a more stable form such as silver iodide ( U.S. Pat. No. 5,246,822).
After processing, the material has to be washed to remove materials generated during the processing and to remove excess colour developing agent and hydrogen peroxide which would cause coloration of the material with time.
Single-use processing systems have been described (Research Disclosure, September 1997, p.638). These can involve the application of solutions to the surface of materials in a way which results in a uniform or image-wise amount of solution being applied. The uniform application of developer to the surface of colour negative paper using ink-jet methods has been described EP Application No. 94201050.5. U.S. Pat. No. 3,869,288 describes the separate application of developer solution components by spraying droplets. U.S. Pat. No. 5,200,302 describes a method of processing involving coating developer to produce a film of processing solution of thickness xe2x80x9cat most 20xc3x97xe2x80x9d that of the dry gel thickness. Uniform application results in low density areas being treated with the same chemical amounts as maximum density areas. When limited amounts of solutions are applied, there is limited opportunity to use the solutions to remove chemicals which are unused or which are generated or released during processing.
A method of removal of organic materials, which does not involve washing the processed materials has been described in PCT GB99/04319. The method involves the use of carbon coated in a gelatin layer on a suitable support. The coating is laminated with the processed material and the carbon used to adsorb the undesirable chemicals which are consequently extracted from the processed material. The amounts of soluble dyes used for sharpness control and the unused colour developer were reduced to low levels by this method.
Wet chemical systems of processing are complicated in order to maintain at a consistent performance level. Also, they are difficult to keep clean. They produce liquid effluent that requires disposal. They usually consist of several treatments in different chemical baths plus a washing or stabilisation stage which is used to remove chemicals which would, if remaining in the image, modify the image over time. The problem to be solved is to provide a means of processing photographic material in a simple process which minimises liquid effluent while ensuring the removal of oxidisable organic chemicals, such as colour developing agents, and peroxide which would otherwise modify the images over a period of time.
The present invention provides a method of producing a photographic image in an imagewise exposed photographic material comprising one or more silver halide emulsion layers which method comprises
developing the material with a developer solution containing a silver halide developing agent,
applying to the surface of the developed material a solution of a sulphite compound that reacts with oxidised developing agent and prevents further development, and
applying to the surface of the developed material a solution of an oxidant that oxidises any remaining developing agent,
wherein said sulphite compound is present in an amount sufficient to react with all the oxidised developing agent and said solutions of sulphite and oxidant are applied to the material by means other than immersion in a tank.
The method of the invention eliminates the need for a wash step after development. No water needs to be supplied or removed from the processor.
The method reduces the number of processing tanks required by avoiding the need for stabiliser and/or wash tanks.
A very low volume of liquid can be employed and the method can be used substantially without effluent being produced.
Developer or developer/amplifier reaction is stopped.
Colour developing agent and/or peroxide are destroyed so that the colour developing agent does not couple with any unused couplers in the material.
The photographic material e.g. paper is stabilised.